package lq20107;

import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();

        int[] a = new int[n];
        for (int i = 0; i < n; ++i) {
            a[i] = sc.nextInt();
        }

        Arrays.sort(a);
        int ans = Integer.MAX_VALUE;
        for (int i = m - 1; i < n; ++i) {
            ans = Math.min(ans, a[i] - a[i - m + 1]);
        }

        System.out.println(ans);
    }
}